I will be voting against the same sex marriage bill tomorrow for a variety of reasons. If I am called to speak I hope to elucidate some of them. Two aspects of the Bill are so important and so compelling, however, I also wanted to write about them here.

My first concern is that I and many others thought the Bill was intended to make the status of marriage equal for same sex couples (SSC) with regard to heterosexual couples (HSC). The Bill does not achieve this; in fact, it legally patronises SSCs and leaves them unequal in law. I cannot vote for that.

My second consideration is that I am happy to declare my interest in the grubbier side of politics and state that one of my big concerns is for my party and my colleagues, which is why I am writing this on the ConservativeHome website and not in a national newspaper.

Let’s talk about sex.

Mt first startling observation upon reading the Bill which was produced only a week ago, is that the adultery provision in the Bill is unequal. A gay man/woman is not required to be faithful in the same was as a heterosexual man/woman. The same sex lobby have stated that they want the same rights as heterosexual couples and to be able to enjoy faithful and committed relationships but this Bill does not require them to make any commitment to faithfulness whatsoever in the way straight couples are required to.

A basic legal requirement of The Marriage Act 1973 is for ‘ordinary and complete sex to have taken place’.

In law, you can only divorce for adultery if your partner has sex with a member of the opposite sex.

When a straight couple marry, they forswear all others. It is a basic marriage vow designed to conform with the Marriage Act. What they are saying is ‘I may find members of the opposite sex attractive from time to time however, I will not stray, for the sake of our marriage I will honour my commitment to us and I promise to forsake all others’.

A gay man or woman won’t have to do this because obviously, he or she isn’t going to find a member of the opposite sex attractive and so the adultery provision is unequal. A gay man/ woman is not required to be faithful in law in the same way a straight man/ woman is. What is marriage without a legal vow of commitment and faithfulness?

Tucked away at the back of the Bill, probably deliberately in order that it will never be reached and debated in committee, is the startling revelation that there is also no obligation for a SSM to be consummated. In a HSM, if a marriage is not consummated it is voidable. This is because sex is the basis of marriage. The law as it stands is very sensible. Whilst marriage is about more than sex, marriage is not about less than sex. Legally, a long-term relationship without ‘ordinary and complete sex’ can be a friendship, a relationship, but it’s not a marriage.

The Government's answer to the consummation question is that SSM cannot be declared voidable as a result of non consummation because the legal definition of consummation is impossible to achieve. The Governments admission that a SSM cannot meet the legal requirement of The Marriage Act makes nonsense of the whole Bill. If there cannot be consummation and thereby legal equality, what is the point of the Bill?

The Bill was intended to treat SSCs on an equal basis with HSCs but actually, if you are in an SSM you don’t have the same legal endorsement; you are the inferior party in a Bill which fails to equally encompass all.

Before anyone reading this thinks I am opposed to supporting same sex couples, I am not. Such a statement could not be further from the truth.

I am however totally opposed to the legal re-definition of marriage.

Now let’s talk about politics.

Having read the briefing from the Catholic Church and Anglican churches to MPs, and if the polling is correct that one in five people who voted for the Conservative Party at the last GE won’t at the next, the passing of this Bill could lose us as many as 100 seats.

The Prime Minister may have made a good speech on Europe which many Conservative MPs support. Europe, however, is not a religion. No one died on a cross for a referendum on membership of the European Union. People of faith may not vote for us again if this Bill passes and a good speech on Europe won’t persuade them to do otherwise.

To highlight how damaging this legislation could be to Conservative MPs, I cite the case of the former MP for Oxford West and Abingdon, Evan Harris. An arch proponent of anti Christian beliefs such as abortion and assisted suicide, Mr Harris lost his 7,683 incumbency padded majority as a result of the church communities in his constituency, led by one single lady vicar, voting against him. For no other reason than that.

When Labour introduced civil Partnerships, they did the right thing, but they wouldn’t touch SSM because they recognised that in their Catholic communities it would have been politically suicidal. If this Bill passes we will hand Labour MPs a great gift as they can simply say ‘it wasn’t us’. Those Labour MPs who are vulnerable will have the luxury of standing back and laughing at loyal Conservative MPs with small majorities as they troop into the lobby and in doing so, save Labour MPs their majorities and political scalps. We will deliver a Bill the Labour party only ever wistfully dreamt about but knew it couldn’t deliver and retain power. Especially without an election manifesto to do so, which of course, we don’t have. Not a single person in the UK voted Conservative in 2010 because we said we would introduce SSM.

I hope to lay down an amendment which will define SSM as state marriage. Gay couples and straight couples are magnificently different, wonderful and all deserving of the deeper love and fulfilment which comes from commitment. We should all be equal in the eyes and provision of the law.